Steps to reproduce: open the bug URL (maybe twice, to load from cache). Results: 100ms and 110ms images are animating synchronously. Testing on a G4/1.25DP. I don't think this is a decoding issue, since a simpler page with only these two images is rendered correctly.
<rdar://problem/5316290>
I could not reproduce this on a MacBook Pro 2GHz.
On my G4, I can reproduce this when running Safari 2 + TOT, but not when running Safari 3 + TOT (in both cases, debug builds). Which probably makes this bug invalid.
Marking invalid per Comment #3.